The present invention relates to plated automotive parts and to methods of plating automotive parts.
As shown in FIG. 1, some automotive parts 10 are conventionally formed of a base metal 12 (e.g., steel) to which one or more layers of nickel (i.e., “Ni”) 14 is/are applied. An outer layer 16 of hexavalent chrome has conventionally been applied to the layers 14 of Ni to complete the plating of the base metal 12.
FIG. 2a details a conventional method of plating parts of the type shown in FIG. 1 with hexavalent chrome. Specifically, in step S101, a base metal 12 is subjected to a pre-degreasing process. In step S102, the base metal 12 is degreased. In step S103, the degreased base metal 12 is subjected to water washing (one or more times). In step S104, the washed base metal 12 is subjected to acid cleaning (i.e., pickling). In step S105, the base metal 12 is again subjected to water washing (one or more times). In step S106, a semi-bright finish layer 14A of Ni is plated onto the base metal 12. The once-plated base metal 12 is then allowed to cool (i.e., recover) in step S107. In step S108, a bright finish layer 14B of Ni is plated onto the semi-bright layer 14A of Ni. In step S109, the twice-plated base metal 12 is again allowed to recover. In step S110, chromium activation occurs. In step S111, an outer layer 16 of hexavalent chromium is plated onto the bright finish layer 14B of Ni. In step S112, the plated base metal 12 is again allowed to recover. In step S113, the plated base metal 12 is subjected to water washing (one or more times). Finally, in step S114, the plated base metal 12 is subjected to hot water washing.
The chrome plating gives the automotive part an attractive appearance and protects the part from scratches and rust because chromium metal has a high surface hardness and excellent wear resistance and corrosion resistance. Hexavalent chromium, however, is a specified toxic substance, and its use requires treatment of wastewater and exhaust air. Thus, manufacturers using hexavalent chromium must invest in, operate, and maintain a detoxification system and must pay additional costs to meet local regulatory requirements.
FIG. 2b details a conventional method of detoxifying wastewater and exhaust air generated during the process shown in FIG. 2a. Specifically, in step S201 (which occurs during and/or after steps S101 to S105 in FIG. 2a), wastewater is treated to remove or neutralize alkali and acid. In step S202 (which occurs during and/or after steps S106 to S109 in FIG. 2a), wastewater is treated to remove or neutralize Ni. In step S203 (which occurs during step S111 of FIG. 2a), exhaust air is treated to remove hexavalent chromium by capturing hexavalent chromium mist released into the atmosphere during chromium plating and depositing the captured hexavalent chromium mist in the wastewater. In step S204 (which occurs during and/or after steps S110 to S114 in FIG. 2a), wastewater is treated by a reduction treatment of hexavalent chromium to trivalent chromium. Finally, in step S205 (which occurs after step S204), other chromium is treated.
Even when the detoxification treatment is strictly managed, the use of hexavalent chromium presents environmental and safety risks. Such risks include leakage of hexavalent chromium from the manufacturing process potentially resulting in air, soil, and/or water contamination and adherence of hexavalent chromium to products potentially creating adverse health effects in persons exposed to the hexavalent chromium.
Additionally, manufacturers desiring to use hexavalent chromium must satisfy local regulatory requirements and obtain approval and licensing to use hexavalent chromium. Obtaining approval and licensing can be a lengthy process and, in some cases, approval may be impossible to obtain. Even if approval is obtained, risks to the manufacturer include production stoppages due to releases of hexavalent chromium, compensation paid to parties injured by hexavalent chromium contamination, and the cost of environmental cleanup due to hexavalent chromium pollution.
Thus, although chrome has proven to be an effective plating material, its use raises environmental concerns. What is needed, therefore, is an automotive plating and method of plating which, like chrome, provides effective plating properties but which is more environmentally friendly than chrome.